libafscp: Fix leak when afscp_ResolvPath errors

libafscp: Fix leak when afscp_ResolvPath errors

If afscp_DefaultCell fails, then afscp_ResolvPath returns without
freeing the memory allocated to 'p' by strdup.

Fix this by adding a free() in the appropriate place.

Caught by clang-analyzer

Change-Id: Ic2691d209c913cd600d9a9a1ebb4614dff35aa3b
Reviewed-on: http://gerrit.openafs.org/9195
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>